Molecular Mechanism Regulating Floral Architecture in Monocotyledonous Ornamental Plants

Abstract

Molecular and genetic analyses of flower development have been conducted primarily in dicot model plants such as Arabidopsis thaliana and Antirrhinum majus. The obtained data are the basis for the ABC model, which was extended to the ABCE model of floral development. This model has been validated in many dicot species using genetic transformation studies and mutant analyses. Many dicot flowers have two distinctive perianth whorls, which include greenish sepals and showy petals. By contrast, the monocot lily flower has two almost identical petaloid whorls, the inner and outer tepals. To explain this type of floral morphology, a modified ABC model, the further extended modified ABCE model, was proposed. According to this model, B-class genes are expressed in whorls 1–3, and whorls 1 and 2 form petaloid structures. This review describes the molecular mechanisms regulating flower development in monocots. Since the showy perianth is one of the most important traits in floricultural crops, we focused on the B- and C-class genes, which are related to the development and modification of the perianth. The review describes the expression patterns of floral organ identity genes, and presents functional studies using double-flowered and viridiflora cultivars in some monocot species. Besides lily-type flowers, there are several types of monocot flower, such as commelina type with two whorls of distinctive perianth, orchid and grass flowers. The review also describes the molecular analyses of these types of monocot flower.